MagnetarTwists:Fermi/GBMDetec5onof

SGR1550‐5418

ErsinGöğüşSabancıUniversity,Istanbul

YukiKaneko

C.Kouveliotou,E.Ramirez‐Ruiz,J.Granot,A.vanderHorst,A.WaYs,A.vonKienlin,etal.

FermiSymposium,Washington,D.C. November4,2009

SGR1550‐5418=1E1547.0‐5408

GBMTrigger090122037

•  Triggerat00:53:52UTonJanuary22,2009

•  1stof41GBMTriggers

•  Triggerdatafor600s

•  58untriggeredburstsiden5fiedwithin600s

EnhancedPersistentEmission

Pulsa5onDetec5on

12-27 keV

27-50 keV

50-102 keV

102-293 keV

TimingAnalysis

PulseProfiles

•  DoublepeakatlowE•  SinglepeakathighE•  Nopulsa5on>110keV

(a) 10 － 14 keV (b) 14 － 22 keV (c) 22 － 33 keV (d) 33 － 50 keV (e) 50 － 74 keV (f) 74 － 110 keV

RMSPulsedFrac5onSpectrum

•  Correlateswithenergy

•  Peaksin50–74keV

•  Notsignificant>110keV

•  Indica5onofa“dip”

SpectralAnalysisTimeIntegratedSpectrum[T0+72–248s]

8–909keVBurstFree

PowerLaw

Addi5onalBlackbody(kT=18keV):ΔCstat=13.5(for2DOF)

TotalEnergy4.3 × 1040 ergs

TimeResolvedSpectra(ν Fν)[T0+72–117,122–169,173–223s]

122–169s 173–223s

PowerLaw

BlackbodyBlackbody

PowerLaw

74–117sPowerLawonly(Blackbodyisnotneeded)

FBB/FTOTAL=26% 25%

TemporalProper+es•  Pulsa5onsmostsignificant

in120–210s

•  Pulsefrac5onpeaksin50–74keV

•  Pulsa5onsnotseenabove110keV

SpectralProper+es•  Blackbodyrequiredin

122–223s

•  BlackbodykT~17keV(Wienpeak~50keV)

•  FBB25%

FPWRL75%

Assumingahotspotofradius RHSontheneutronstarsurface

For D =5kpc,kT=17keV:

AHS≈ 0.044(D/5kpc)2km2

RHS≈120m

Hot Spot

Corona on Magnetars by Beloborodov & Thompson (2006)

Dissipation rate: Ld ~ Ι ΦE Net current: Ι ∝ Β, Δψ, a2

Lobs = 2.8 × 1038 erg s-1 >> Ld

inconsistent with observation

e± plasmas & photons confined by closed B field region

Trapped energy: EB(a) = 1/6 a3B2 > Eiso,BB

For a = 120 m & Eiso,BB= 5.6 × 1040 erg: B > 1.4 × 1014 G

consistent with B = 2.2 x 1014 G from PP

Energy dissipated in the corona is radiated in two forms:

  non-thermal, high energy radiation produced by collisionless dissipation of the coronal beam

  blackbody radiation by thermalization: as the remaining energy dissipated in the corona enters the dense atmosphere, the crust is thermalized by two-body collisions and e-/e+ pair formation

Both components are expected to have comparable luminosities.

Assumingahotspotofradius RHSontheneutronstarsurface

For D =5kpc,kT=17keV:

AHS≈ 0.044(D/5kpc)2km2

RHS≈120m

whichisthesizeofthemagne+cally‐confinedhotplasmaandis<<1%oftheNSsurfacearea

Hot Spot